| Against the backdrop of global warming,various natural disasters have become more frequent,and drought is one of the most severe ones that causes numerous adverse impacts on the economy,society,and the environment.The Huang-Huai-Hai Plain is located in a warmtemperate semi-arid and semi-humid monsoon climate zone,with mountains in the northern and western edges and plains in the central and eastern parts.It is not only the political,economic,and cultural center of China but also an important commodity grain production base.However,there are differences in the multi-scale spatiotemporal distribution of precipitation,resulting in frequent droughts,severely affecting the development of the national economy.Therefore,it is of great significance to analyze the spatiotemporal evolution characteristics and causes of meteorological drought in the Huang-Huai-Hai Plain for regional drought analysis and prevention.This article is based on meteorological data from 56 meteorological stations in the HuangHuai-Hai Plain from 1961 to 2019.The best meteorological drought index was selected,and methods such as Arc GIS spatial interpolation,wavelet analysis,EOF analysis,and Copula joint function were used to study the spatiotemporal variation characteristics of meteorological drought in the Huang-Huai-Hai Plain.Combined with meteorological elements,climate factors,terrain factors,and land use data,Pearson correlation analysis and cross-wavelet analysis were used to explore the influencing factors of drought changes in the Huang-Huai-Hai Plain.The results are as follows:(1)Based on precipitation data and the Meteorological Drought Atlas,the study investigated the spatiotemporal characteristics and applicability of drought indices for meteorological variables.The results show that precipitation,temperature,and potential evapotranspiration exhibit uneven spatiotemporal distribution in the Huang-Huai-Hai Plain.During drought years,SPEI can provide timely reflection of different types of drought,and it performs well in capturing the spatial distribution of seasonal and interannual droughts.However,SPI and RDI show varying degrees of lag or lead in characterizing drought,and they also have biases in reflecting the severity of drought.(2)By calculating the frequency of different levels of drought at different time scales and conducting spatial interpolation,and by using wavelet analysis for periodicity and SR for drought trend analysis,the results show that: at the monthly scale,light and moderate droughts are the main types of drought,followed by severe droughts,while extreme droughts have the lowest frequency of occurrence.The frequency of occurrence of various drought types at the seasonal scale is consistent with that at the monthly scale.The periodicity analysis shows that the study area undergoes multiple cycles of wet and dry changes in different months and seasons.Moreover,there are differences in the future short-term wet-dry changes.The first principal cycle of the annual SPEI is 9 years,with significant droughts occurring around 1991 and 1966,and a relatively humid year in 1964.The study area is currently in the early stage of drought,and the drought is expected to continue for some time.SR drought trend analysis shows significant wet-dry changes occurring in June,August,and October,while the drought change trend and significance differ in different seasons.The wet-dry change trend is not significant at the annual scale.(3)EOF analysis was used to decompose the meteorological drought fields at different time scales and study their dry/wet variation.The results show that there are differences in the dry/wet changes among different months and there are different sensitive centers,and the corresponding time coefficients can represent the dry/wet conditions and future changes.The dry/wet changes in the whole region are consistent in the months of January to June and August to December,and the sensitive centers for dry/wet changes all include the area around the Qinglong station.In July,the dry/wet changes in the whole region are opposite,with the north being positive and the south being negative.Except for the summer,the dry/wet changes in the other three seasons are consistent in the whole region.The dry/wet changes are opposite in the summer,and the dry/wet alternation is most frequent in the winter,followed by the summer and spring,and the dry/wet alternation is the least in the autumn.At the annual scale,the dry/wet changes in the whole region are consistent,and the dry/wet alternation is relatively frequent.(4)The optimal distribution function of drought characteristics was evaluated and the distribution patterns of coincidence return periods and joint return periods were studied.The results showed that for the various drought events with a duration of 2 months in the HuangHuai-Hai plain,the average mild drought had a distinct high coincidence return period region in the Yiyuan and Qinhuangdao stations;the spatial distribution of the average moderate drought and severe drought was low in the west and north and high in the east and south.The spatial distribution characteristics of the various drought events with a duration of 3 months were basically similar,and the high and low coincidence return period regions were also similar to those of the drought events with a duration of 2 months of the same drought level.For the various drought events with a joint return period of 2 months,the high-value regions of the average mild drought,moderate drought,severe drought,and extreme drought were concentrated in the northeast,northwest,and southwest regions.For the various drought events with a joint return period of 3 months,the high-value regions of the average moderate drought and severe drought were mainly distributed in the northwest,southwest,and the Tai’an station area in the east.(5)Through Pearson correlation analysis and cross-wavelet analysis,the correlation between SPEI and various influencing factors was studied.The results show that precipitation,temperature,and potential evapotranspiration are closely related to meteorological drought,with precipitation being the main influencing factor.The response of SPEI to various meteorological factors is most pronounced in spring and summer,followed by autumn,and weakest in winter.There are differences in the main topographic factors that have the greatest impact on different levels of drought,and the main research periods influenced by various topographic factors are different under different drought frequencies.The impact of atmospheric circulation factors and solar black spots on drought varies over time,and the main influencing factors during different periods of the year are different.IPO,SOI,and Ni?o3.4have high correlations with SPEI and cover a long period,and their impact on drought is prominent.The reduction of farmland area is the largest land use change,followed by the increase in impermeable surface area,which mainly comes from the transformation of farmland,followed by grassland and water area.The increase in impermeable surface area and the significant reduction in farmland,grassland,and shrub areas provide conditions for the occurrence of drought. |
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